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  1. #41
    Join Date
    Sep 2008
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    Omaha, NE
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    Not sure if this has been mentioned ( i didn't read the entire thread) But the NHRA won't allow any MIG welding except where the plate (mount) of the cage attaches to the unibody or frame rails. However on SCCA cages you can MIG the entire thing together in most classes. Everythign I did read was good advice so i just wanted to throw this out there in case you hadn' heard these yet
    Dynasty 200DX
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  2. #42
    Join Date
    Dec 2007
    Location
    Baldwin, NY
    Posts
    275

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    Quote Originally Posted by turboglenn View Post
    Not sure if this has been mentioned ( i didn't read the entire thread) But the NHRA won't allow any MIG welding except where the plate (mount) of the cage attaches to the unibody or frame rails. However on SCCA cages you can MIG the entire thing together in most classes. Everythign I did read was good advice so i just wanted to throw this out there in case you hadn' heard these yet

    Nope, NHRA does allow mig welding on mild steel,

    "All 4130 chromoly tube welding must be done by approved TIG heliarc process; mild steel welding must be done by approved MIG wire feed or approved TIG heliarc process."
    Voigt Precision Welding, Inc.

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  3. #43
    Join Date
    Sep 2008
    Location
    Omaha, NE
    Posts
    447

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    Quote Originally Posted by Badd00SS View Post
    Nope, NHRA does allow mig welding on mild steel,

    "All 4130 chromoly tube welding must be done by approved TIG heliarc process; mild steel welding must be done by approved MIG wire feed or approved TIG heliarc process."
    Ahh.. I must have grouped mild in with 4130, i'd just enver make a cage from mild if i was going under 12 seconds in the 1/4
    Dynasty 200DX
    Hobart Handler 135
    Smith MB55A-510 O/A setup
    Lathe/Mill/Bandsaw
    Hypertherm Powermax 45
    Just about every other hand tool you can imagine

  4. #44
    Join Date
    Dec 2006
    Posts
    612

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    There's nothing unsafe about a sub 12 sec. mild steel chassis. In many cases the weight savings MS to CM isn't significant enough to warrant the extra cost of CM. It all depends on the application.

  5. #45
    Join Date
    Mar 2009
    Location
    Corona, CA
    Posts
    213

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    Id have to agree with that...nothing unsafe about mild steel. Didn't the OP say something about road racing though?

    CM is stronger yes...but go back to high school chem for a second for me...you gain one property and you sacrifice or otherwise compromise for that property.

    Mild steel is more malleable...it will bend before it shears/cracks/snaps in half.

    CM is more brittle...vibrations will crack it if they are severe enough. It is however as strong as mild steel, with less wall thickness.

    Even some GT2 and GT1 class road race cars/teams (2000-2600lbs with up to 650hp) use mild steel in their cages...its all about geometry. The material helps, but the geometry is really what makes the cage.

    I dont know the exact number of bars in the cars such as the Corvette Racing Vettes...but I know that it is over 20, at least. Even spec miatas have at least 11 to 12.

  6. #46
    Join Date
    May 2009
    Location
    Texas
    Posts
    7

    Default SCCA rules for roll cages, etc.

    I am an SCCA tech inspector that has seen some VERY bad welds. First, in the SCCA General Competition Rules (GCR) the roll cage tubing size is determined by the car weight and class. In the case of Spec Miata the minimum size is 1.5 x .095 DOM tubing- NO ERW. These rules take bends into account. The bends must be a minimum of three times the diameter of the pipe. The number of attachment points is determined by the car class, in my case STU is limited to eight. The maximum area of attachment plate in all planes is 144 sq. in. and the maximum thickness this year is 1/4 in. (After several SM's put 1 in. plate in the right rear to get better corner weights.)

    Wall thickness can now be measured with an ultrasonic thickness tester BUT, as was mentioned, it can be difficult to use properly. If the wall thickness is measured by drilling a hole make sure the bit does not strike the far wall as that will make the measurement too thin. Maximum hole size is 1/4 in., 3/16 in. preferred and anything smaller will not accept the depth rod of the caliper.

    Second, all points mentioned about practice are good. In my case practice doesn't seem to help and I will have a professional welder do all the welds except for the attachment plates. I would definitely recommend building the cage but having a professional welder do all the tubing joints. If possible get a tech inspector to recommend a welder because not all road race car shops have good welders. If a car builder insists on welding his own cage I recommend going to a Community College welding program. He should also cut apart his practice joints to check for penetration, etc.

    Gussets have not been mentioned but I highly recommend them. My car will have the maximum number of gussets per joint allowed which is two (SM is also two but other classes have no limits). Also any number of braces are allowed as long as they attach to only the attachment plates or the cage tubing and triangulation really helps.

    Finally, what ever competition you are in be sure and get the rules, read them and ask questions before doing something that might have to be undone. If you ever think that you might change classes or sanctioning bodies try to prepare the car so that you don't have to tear every thing out and start over. We had a lawyer that thought he could do his own thing and found out that he couldn't change the rules to suit him.

    John Cooper
    SCCA national license tech
    Millermatic 250X
    1985 Toyata MR2 being prepared for STU

  7. #47

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    John,

    So.... what do you do when someone shows up with their fresh cage that they just paid 3-4K for and is nothing but booger welds and missed backside welds???

    Always wondered how these cars get through SCCA tech. I've just become a NASA tech shop and I'm really not looking forward to explaining to Joe Racer how he just paid for a scrap heap from another shop.
    Scott Rhea
    It's not what you build...
    it's how you build it
    Izzy's Custom Cages

  8. #48
    Join Date
    Jan 2008
    Location
    VA
    Posts
    298

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    Quote Originally Posted by Speed Raycer View Post
    John,

    So.... what do you do when someone shows up with their fresh cage that they just paid 3-4K for and is nothing but booger welds and missed backside welds???

    Always wondered how these cars get through SCCA tech. I've just become a NASA tech shop and I'm really not looking forward to explaining to Joe Racer how he just paid for a scrap heap from another shop.
    In the case of PCA it is what you don't do. You don't issue a log book. I have only had one poor looking welds car presented for a log book but have seen plenty of cages that could have been thought out a bit better. Pro shop and home built alike. Some of the most well thought out cages were home built. I guess when it is your can in the seat you sweat the details.
    Weekend wannab racer with some welders.

  9. #49
    Join Date
    Mar 2009
    Location
    Corona, CA
    Posts
    213

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    Izzy,

    I think I've seen some of your work on 7 Club, Id swear I've been to that website before.

    You have to tell him that he needs to have those welds fixed if you deem it unsafe. And that you wont give him a log book till he does. If he wants...he can go to another inspector to see if they'll sign off on it...but always CYA first.
    Precision is only as important as the project...if you're building a rocket ship...1/64" would matter. If you're building a sledgehammer...an 1/8" probably wont.

  10. #50

    Default

    Sorry, I should have been more specific. What do you do when it's already logbooked and just swinging by for the annual?

    I have no qualms about letting someone know that there's some subpar work that needs to be fixed. I've had several come in for updates that have had horrible or missing welds from some well known shops. Just haven't done it officially yet where I'm telling someone "nope, you can't race this weekend until you have this fixed"

    Fire... I used to post over at 7club quite a bit. Sold my 1st Gen about 2 or 3 seasons ago so I don't get back there much.
    Scott Rhea
    It's not what you build...
    it's how you build it
    Izzy's Custom Cages

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